The umbridrome (/ˈʌmbrɪdroʊm/) is a large, asphalt-bodied stranger. Although it has the superficial appearance of lips, it has no mouth or other internal structure. It is solid throughout, and the variegated coloration of its black and gray stripes reflects different compositions of grit and gravel. Its body connects to pavement, consisting of a head and three to six tendril-like limbs that are fully contiguous with the surface on which it appears, and thus cannot be dug out to reveal a larger build. It is rough to the touch, and feels approximately 3-5°F warmer than its surroundings. Its odor is strong and tarry.
The umbridrome possesses no identifiable difference from typical asphalt, and has no regenerative ability.
The umbridrome appears on blacktop, from which its head rises upwards, as though surfacing from beneath the face of an opaque lake. Due to its almost nonexistent stability, the umbridrome is unable to survive the process of its generation, and never emerges fully from the earth. It dies within less than a minute of generation, with its corpse remaining as a hard monument.
Groups of umbridrome appear in various non-linear formations, with scattered clusters being more common, and circular formations being most rare.
Their corpses remain for anywhere from three days to five months, until they crack apart suddenly and completely, leaving behind a pile of tarry chunks and pebbles.
The appearance of any umbridrome circle, regardless of the number of individuals, increases the stability of other strains within 9,999 feet, with this stabilization remaining noticeable for several months following the umbridrome's deaths. Pockets of erratic sub-strains die off and coalesce into more stable strains, which may resemble their distant antecedents.